This invention relates to a head adjusting disk adapted to adjust the position of a head in a floppy disk drive mechanism or the like.
In apparatus in which a floppy disk is used, such as, for example, word processors which exhibited wide spread in recent years, a floppy disk on which data are written must be able to be used on a same data recording device at least of the same type. To this end, at least mounting conditions of a head on a floppy disk drive mechanism must be the same for apparatus in which the same type of floppy disks is used.
Conventionally, adjustment of mounting conditions of a head is conducted in a quality controlling step in a production line. Thus, fine adjustment of a head which has been adjusted temporarily in prior is effected using a head adjusting disk on which a reference record track is formed.
Adjustment of the position of a head is especially important among adjustments of mounting conditions of such a head. This is an adjustment in which an error of the position of a head mounted in a radially inward or outward direction from a designated position is adjusted. As a method of such adjustment, it is known to use an eccentric annular track.
FIG. 1 is an illustrative view showing an example of a head adjustment disk used for such a head position adjusting method. Referring to this figure, reference character 1 designates a head adjusting disk, 2 an index hole, 3 and 4 designate each a head position adjusting record track, 5 designates a locus of a head to be adjusted, O the center of rotation, and A an eccentric center.
Referring further to FIG. 1, the index hole 2 in the form of a perforation is formed in the head adjusting disk 1 at a position spaced a predetermined distance from the center of rotation O of the disk 1. The head position adjusting record tracks 3, 4 (hereinafter referred to simply as record tracks) are formed in concentrical annular configurations having their centers at the eccentric center A on a straight line X--X' which interconnects the center of rotation O and the index hole 2.
Locations of the record tracks 3, 4 are designed in the following way. If the head adjusting disk 1 is mounted on a turn table (not shown) and is rotated in a direction of an arrow mark B around the center of rotation O, then the record tracks 3, 4 will naturally be in eccentric positions.
Meanwhile, adjustment of the position of a head is commonly effected so as to bring a head (not shown) into precise coincident with a record track which is located at the center of a recording area of a floppy disk (this record track will be hereinafter referred to as a central record track). Locations of the record tracks 3, 4 are determined such that, if a locus of the head where the head is precisely coincident with the central record track is indicated as the locus 5, the locus 5 coincides with the record track 4 at a point P on the line X--X' on the same side as the eccentric center A relative to the center of rotation O while it coincides with the record track 3 at a point Q on the line X--X' on the opposite side to the eccentric center A relative to the center of rotation O.
Then, if the adjusting disk 1 is rotated to effect scanning for reproduction with a head the position of which has been temporarily or roughly adjusted, then signals recorded on the record track 3 and signals recorded on the other record track 4 will be reproduced with a time lag during rotation.
FIGS. 2A and 2B are diagrams showing waveforms of reproduction signals obtained from the record tracks 3, 4 of FIG. 1. If it is assumed that signals in a period of time T1 are reproduction signals from the record track 4 while signals in a period of time T2 are reproduction signals from the record track 3, then FIG. 2A shows reproduction signals when a head to be adjusted is properly adjusted in position while FIG. 2B shows reproduction signals when a head to be adjusted is displaced radially inwardly of the head adjusting disk 1 from a proper position to which the head is to be positioned.
In particular, if a head to be adjusted is at a proper position, a scanning locus thereof corresponds to the locus 5 as shown in FIG. 1 and thus coincides with the record track 3 at the point Q while it coincides with the record track 4 at the point P. The record tracks 3, 4 have signals of a same fixed frequency recorded with the same intensity thereon, and hence envelopes of signals in a period T2 in which reproduction is effected from the record track 3 will be the same as envelopes of signals in a period T1 in which reproduction is effected from the track 4.
On the other hand, if the head to be adjusted is displaced radially inwardly of the head adjusting disk 1, the head to be adjusted is displaced from the record track 3 so that peaks of envelopes of signals in a period T2 in which reproduction is effected from the record track 3 will be reduced, as seen from FIG. 2B. Further, the head to be adjusted crosses the record track 4 twice, and peaks of the reproduction signals hold their maximum within this portion of a period T1. On the contrary, if the head to be adjusted is displaced radially outwardly of the head adjusting disk 1, peaks of the reproduction signals will hold their maximum in a period T2 during reproduction from the record track 3 while peaks of signals will be held low in a period T1 during reproduction from the record track 4, on the contrary to FIG. 2B. Accordingly, the extent and direction of displacement of a head can be detected with high accuracy from a ratio of peaks (lobe ratio) of signals in periods T1 and T2, and precise adjustment of the position of a head can be attained, accordingly.
By the way, in a method of adjusting the position of a head using such a conventional head adjusting disk, signals reproduced from record tracks 3, 4 must be distinguished from each other, or else, the direction of displacement of the head to be adjusted cannot be discriminated.
Therefore, it has been common to produce signals presenting the reference of time in synchronism with scanning for reproduction of record tracks 3, 4 in order to discriminate individual reproduction signals from relationships of time of the signals relative to the reference time signals. In order to produce such reference time signals, a method is conventionally employed to detect the index hole 2 of FIG. 2.
In particular, a disk drive mechanism is provided with an optical means including a light emitting diode and a phototransistor for detecting an index hole 2. Now, if it is assumed that the index hole 2 is detected to provide a corresponding pulse signal (hereinafter referred to as a hole signal) when a head to be adjusted is positioned at a point R on a line Y--Y' which is perpendicular to the line X--X' relative to the head adjusting disk 1, then from the reference of time presented by the hole signal, signals are first reproduced from the record track 4 and then signals are reproduced from the record track 3. Accordingly, order of reproduction signals from the record tracks 3, 4 is determined relative to the hole signal, and thus discrimination of both signals can be enabled thereby.
In this way, adjustment of the position of a head to be adjusted is enabled with high accuracy. However, in a conventional head adjusting disk, a record track which is located in eccentric relationship relative to the center of rotation must be formed with high accuracy. Thus, in order to form such a record track on a head adjusting disk, a special disk eccentric drive mechanism is necessary. Besides, such a record track must be formed with high accuracy such that, when a head to be adjusted is placed in a proper position, the locus 5 of the head to be adjusted must be completely coincided with the eccentric tracks each at just one point (points P and Q). But, it is very difficult to form such eccentric tracks with high accuracy on the head adjusting disk. Accordingly, the conventional method has a defect that a large error inevitably appears to such eccentric record tracks, which will deteriorate accuracy of adjustment of the position of a head. Although it is possible, when the position of a head is to be adjusted, to eliminate influence of such an error, time and labor therefor cannot be avoided to become extremely great.
Also, in adjustment of the position of a head using a conventional head adjusting disk as described above, it is common to compare peaks of waveforms of reproduction signals from the recording head 3, 4 (FIG. 1) with eyesight. As a result, adjustment of the head position may be accompanied by exhaustion, and besides accuracy must be questioned.
Further, it is necessary for a disk drive mechanism to be provided with means for detecting an index hole. Thus, a disk drive mechanism must include means which has no direct connection with data writing and reading operations to and from a floppy disk. Moreover, it is disadvantageous in that, in a disk drive mechanism which has no such index hole detecting means, reproduction signals from record tracks 3, 4 cannot be distinguished from each other, and as a result, the position of a head cannot be adjusted.